\begin{tikzpicture}[
    node distance = 2cm and 2cm,
    N/.style = {circle, draw, font=\Large, minimum size=1.1em},
    every edge/.style = {draw, -> , semithick, shorten >=2pt},
    every edge quotes/.style = {auto=right, inner sep=2pt}
    ]
    \node [N] (1) at (0,0) [label=left:{+\textcolor{red}{-}}] {1};
    \node [N] (3) [right of =1] [label=below:{\textcolor{red}{+}}] {3};
    \node [N] (4) [right of =3] [label=right:{\textcolor{red}{+}-}]{4};
    
    \path (1) edge [->] node [above] {b} (3)
    (3) edge [->] node [above] {c} (4)
    (1) edge [loop above] node [above] (a) {a} (1) %循环
    (4) edge [bend left] node [below] (e1) {$\varepsilon$} (3) %两个节点之间
    (1) edge [bend left] node [above] (e2) {$\varepsilon$} (4); %两个节点之间 长 上
    
    \draw[red] ([xshift=-0.75em,yshift=0.75em+0.5em]e1.center)--([xshift=0.75em,yshift=-0.75em+0.5em]e1.center);
    
    
\end{tikzpicture}
